This invention is concerned with impact tools and more particularly with the attachment of the handle to the head of the tool.
In conventional hammers employing wooden handles, an end portion of the handle is inserted into the tapered eye of the head and wedges are driven into the terminal surface of the end portion so as to expand the handle into the eye. One problem with this mode of attachment is that the wood of the handle must necessarily be split to receive the wedges, weakening the handle. Another problem is that the handle tends to loosen after the tool has been used for a while. Handles are also secured to the heads of impact tools by adhesives, such as epoxy resins, but this technique requires careful preparation of the parts to insure cleanliness and a strong bond. Metal handles are attached to the heads of impact tools by special expansion techniques which are limited in application and which are expensive.
It has also been proposed to attach the handle to the head of an impact tool by means of pieces or inserts fitting between the sides of the handle and the corresponding side surfaces of the head eye. For example, U.S. Pat. No. 255,166 issued to Hardie discloses an arrangement in which the end portion of the handle is inserted through and projected far beyond the eye of the head. Then wedge pieces are fitted to the sides of the end portion, each piece having a protrusion which fits within a corresponding notch of the handle. Then the assembled wedge pieces and handle are driven back into the eye of the head. A problem with this arrangement is that much of the handle material must be removed to provide the notches which lock the wedge pieces to the handle, significantly weakening the handle, and the wedge pieces must be carefully tailored to the handle so that the necessary wedging action is obtained.
U.S. Pat. No. 241,647 to Grellner discloses an arrangement in which S-shaped pieces secure a handle to a head having an eye with a special shape to receive the attachment pieces. This arrangement clearly has no general utility.
U.S. Pat. No. 1,508,874 to Christensen discloses an arrangement in which pieces fit between the sides of the handle and the associated sides of the eye, the pieces being provided with projections to lock over the edges of the inner and outer openings of the eye, and in some cases the inner ends of the attachment pieces are secured to the handle by a bolt or rivet. This arrangement requires peculiarly shaped fastening pieces, is difficult to effect, or requires weakening of the handle to receive a rivet or bolt. In the absence of the rivet or bolt, the attachment of the handle to the head by wedging action is deficient.
Swiss Pat. No. 150,381 (1932) to Kunz, French Pat. No. 1,038,020 (1953) to Perrin and Fr. Pat. No. 737,291 (1932) to Fouquet teach other arrangements for securing the handle to the head of an impact tool, but these arrangements suffer from various deficiencies and none is of general utility. Although Fr. Pat. No. 737,291 discloses the broad use of shock absorbing elastomeric material, and such material is preferably utilized in the present invention, the environment in which that material is used (the fastening technique) is entirely different from the present invention as will be seen hereinafter.